[3. Longest Substring Without Repeating Characters](https://opposite-wallet-8b6.notion.site/3-Longest-Substring-Without-Repeating-Characters-93f4441a29e446a981772f31e7b01d53)

[5. Longest Palindromic Substring](https://opposite-wallet-8b6.notion.site/5-Longest-Palindromic-Substring-bb226352cd664bffbac375088748a596)

[6. Zigzag Conversion](https://opposite-wallet-8b6.notion.site/6-Zigzag-Conversion-d60c7613265740f7a696919d4043c48f)